Cable dressing means



A. S. APA ET AL Get.

CABLE DRESSING MEANS 2 Sheets-Sheet 1 Filed Feb. 1, 1966 INVENTORS ARMAND SAMUEL APA E v 2 M Mr H WW E 6/ OW E G Y B 0d. 17, 1967 A. s. APA ET AL CABLE DRESSING MEANS 2 Sheets-Sheet 2 Filed Feb. 1, 1966 INVENTORS ARMAND SAMUEL APA Games WILUAM ZWGLERIJR. BY W M W United States Patent 3,346,949 CABLE DRESSING MEANS Armand Samuel Apa, Camp Hill, and George William Ziegler, Jr., Carlisle, Pa., assignors to AMP Incorporated, Harrisburg, Pa.

Filed Feb. 1, 1966, Ser. No. 524,215 8 Claims. (Cl. 29-560) This invention generally relates to cable dressing means, and particularly relates to methods and apparatus for cutting and dressing coaxial cable prior to its termination to connectors.

Cable referred to in the present application has a solid outer conductor formed of aluminum tubing with a solid or tubular copper inner conductor surrounded and held by a dielectric material such as foamed polyethylene. Other coaxial cables of this general type are equally adapt-able to use with the present invention.

The continuing expansion of the use of the so-called radio frequency signals has raised certain criteria which must be met by connectors capable of handling the higher frequencies. Among these are the requirements that a connector not introduce distortion into the signal path of a cable such that that the resultant intelligence content of the signal is altered appreciably. A further requirement is that a connector have characteristics such that signal losses are minimized. A standard measurement is the VSWR test. If a connector has a relatively low flat VSWR over the total frequency range through which the connector is designed to operate, then it may be considered as satisfactory, electrically.

A connector which meets the above requirements is disclosed in my patent application, Ser. No. 308,265, Coaxial Connector, which is assigned to the present assignee.

With suitable connectors, e.g. as disclosed in the above patent application, secured to the ends of cables and subsequently interconnected, the intelligence content of the signal may still be altered appreciably, particularly at the ends of the cables where they join the connectors. It is necessary that the ends of the cables be carefully cut at right angles to the cable axis, the center conductor be aligned relative to the cable shield and all burrs removed from the severed end. This can be accomplished easily in a shop by utilizing tool room machinery such as lathes, drills, etc., but has been extremely difficult and time consuming to accomplish away from a shop, e.g. in the field.

Further requirements have arisen in radio frequency applications wherein cable and/or connectors must be tested for precise signal phasing. Among these requirements are that certain premeasured sections with tolerances to Within .001 inch must be cut from a length of cable. This is extremely ditlicult and often impossible to accomplish in the field because no tolerance deviations are allowed.

It is further required, particularly in high voltage radio frequency connectors, that the voltage break-down path between center and outer conductors be increased. This is accomplished by forming a precisely located circular slot in the cable dielectric at the cable end. A bushing may then be utilized in this slot when a connector is assembled to provide an extended path of resistance between the conductors enabling operation of the connector at considerably higher voltages.

Further requirements in connections of the type above are that the center conductor be precisely aligned relative to the longitudinal axis of the cable. The end of the cen ter conductor must sometimes be drilled and subsequently tapped so that conductor coupling members may be threadably secured thereon. In cables having tubular center conductors, tap drilling is not usually required.

It is therefore a primary object of the present invention to provide new and improved means for dressing metallic sheathed coaxial cables prior to their termination to connectors.

Another object is to provide a cutting device by which the ends of shielded cable may be quickly, easily and accurately cut.

Another object is the provision of a cutting device with a replaceable micrometer attachment by which precise sections may be cut from a length of cable.-

Another object is to provide a cutting device with replaceable means for accurately positioning the inner conductor of the cable for performance of drilling and thread tapping operations thereon.

A further object is to provide replaceable means in a cutting device for cutting select slots in the dielectric at the end of a cable.

A still further object is the provision of a cutting device which is usable at any point along a length of cable and which is applicable to other uses such as cutting conduit or tubing.

A preferred device in accordance with the invention provides a fixture block with caps which secure the block to a cable. A transverse slot is formed into the block to accommodate a saw blade for cutting the cable. One end of a passageway in the block is threaded to accommodate drill and tap jigs having ex-turned threads thereon. Also provided is a micrometer attachment which fastens to the end of the fixture block. The anvil of the micrometer attachment is movable from the saw slot towards the attachment so that precise sections may be measured and cut from the end of a cable. Also provided is a cut-01f attachment which fastens to the end of the fixture block and which positions a cable so that a section of the shield and dielectric may be removed thus exposing a premeasured length of the center conductor. The device is easily removed from a cable by removing the caps from the fixture block.

In the drawings:

FIGURE 1 is an exploded perspective View of a fixture block in accordance with the invention;

FIGURE 2 is a front sectional view of the device secured to a cable;

FIGURE 3 is a view similar to that of FIGURE 2 but showing the center conductor of a cable being aligned and drilled;

FIGURE 4 is a sectional view showing a conductor thread tapping operation;

FIGURE 5 is a sectional view showing the cable dielectric cut-ting operation;

FIGURE 6 is a sectional view of a fixture block and a micrometer attachment in operation;

FIGURE 7 is a sectional view of a fixture block with a cut-off attachment fastened thereon; and

FIGURE 8 is a persepective view of the attachment of FIGURE 7.

Referring now to FIGURE 2, a common type of shielded cable used in radio frequency applications comprises a solid outer conductor 2 formed of aluminum tubing or other suitably conductive metal with a solid or tubular copper inner conductor 4 surrounded and held by a foamed polyethylene dielectric 6. It can be seen that such a cable is difficult to cut so that its blunt end is at a'precise right angle to the cable axis. It can also be appreciated that a cable such as this would have resultant burrs particularly around the center conductor after a cut is made. These burrs are normally hard to remove without appreciably nicking the center conductor or the cable dielectric. Such nicks would subsequently affect the signal through the cable.

Referring now to FIGURE 1, a fixture block assembly in accordance with the invention comprises a rectangular block 8 having a cable receiving passageway 19 longitudinally therethrough. A saw receiving slot 12 which is transverse to and deeper than passageway is formed in block 8. That portion of the curved floor of recess 10 which is located between slot 12 and the forward end of block 8, characterized by the numeral 14, has inturned threads. This arrangement along with a cap 18 permits associate jig members to be threadably received in the end of the block 8.

Cap 18 is generally T-shaped in cross section, the wings 20 and 22 of which abut the top surfaces 8 of upstanding walls 19 and 21 of block 8. The body 24 of cap 18 projects away from the cap proper, and is adapted to extend into recess 10 of the block. The end of body 24 is machined to a semicircular concavity and is threaded so as to form a threaded cylindrical opening 25 in the end of the block when the cap is secured thereto. Machine screws 26 are used in associate holes 28 and 29 to fasten cap 18 to the block.

Another cap 16, which is of the same general configuration as cap 18, is secured to the block directly behind slot 12. Cap 16 is fastened by screws 26 and associate holes 28' and 29 in the same manner as cap 18. The extending end 23 of body 24 is also formed to a semicircular concavity, but is not threaded, as is the end of body 24. End 23 conforms around a cable when cap 16 is tightened onto block 8. Cap 16 constitutes a holding means for locking the block assembly to a cable. With both caps 16 and 18 in place on block 8, a space S remains by which a saw blade may be entered into slot 12 of the device to subsequently cut cable.

Referring now to FIGURES 2, 3 and 4, a drill jig 30 and tap jig 32 are provided for dressing inner conductor 4 of a cable. Jig 30 is generally cylindrical in shape and has ex-turned threads on one end thereof which engage the threads of opening 25. A central passageway 36 is formed through jig 30 so as to receive and guide a drill bit 34. At the exit of passageway 36, leftwardly in FIG- URE 2, is a lip portion 38 which projects from jig 30 and which surrounds and wipes. the end of conductor 4 when jig 30 is threaded into a block 8. Lip 38 has inner walls 39 which diverge from the end of passageway 36 thus formingin effect a bell mouth. Walls 39 simultaneously align the end of conductor 4 and wipe away burrs therefrom as jig 30 bottoms in opening 25. With jig 30 in place, a drill bit 34 is concentrically guided into inner conductor 4, FIGURE 3, for the purpose of drilling the end of the conductor.

Referring particularly to FIGURE 4, a thread tapping jig 32, which is identical to jig 30 except for its larger central passageway 40, is provided for the purpose of concentrically guiding a tap 42 into conductor 4 so that the conductor may be internally threaded. A contact for carrying electrical current from one cable to another may then be threaded into conductor 4.

Referring now to FIGURE 5, a rotary cutter 44 is provided for the purpose of cutting a slot 46 in the end of cable dielectric 6. A bushing (not shown) is subsequently disposed in slot 46 when a high voltage connector is assembled to the cable to provide an extended path of resistance between inner conductor 4 and cable sheath 2. Cutter 44 has a barrel on one end thereof which is machined so as to incorporate. a series of equidistantly spaced cutting blades 47. The outside diameter of barrel 45 is slightly less than the inside diameter of opening 25 so that cutter 44 is rotatable therein. The other end of cutter 44 has a shaft 48 adapted to be secured in a drill chuck. Cutter 44 is entered into opening 25 and bottomed against the end of a cable. During bottoming, blades 47 cut slot 46 in the cable dielectric.

Referring now to FIGURE 6, a micrometer attachment 50 .is provided for the purpose of removing predetermined lengths from the end of a cable. This is required, as set forth hereinbefore, when testing cable for precise signal phasing. Attachment 50 includes a yoke body 51, one end of which is secured to block 8 by means of screws 52 which extend through the end and into associate threaded holes 53 in block 8. A micrometer barrel 54 is fixed to the other end of yoke 51 by means of a threaded bushing 55. The micrometer spindle 56 extends towards the open end 57 of yoke 51, and its barrel 54 and thimble 58 extend away from the yoke, FIGURE 6. In the use of attachment 50, yoke 51 is secured to block 8 as described above whereafter the end of spindle 56 is positioned against the end of a. cable. Spindle 56 is backed away from the cable the exact distance, minus the width of the saw blade used, corresponding to the lengthof section desired to be removed from the cable. Block 8 is loosened from the cable by loosening screws 26 and 26, and, subsequently moved further onto the cable until spindle 56 again abuts the cable end. Screws 26 and 26. are again tightened whereafter a saw blade, not shown, is used in slot 12 to cut that exact length from the cable. It should be noted that attachment 50 may only be used at the end of a cable. It should also be noted that the assembly of the thimble 58, barrel 54 and spindle 56 of attachment 59 are commercially available items adapted to be secured to yoke body 51.

Referring now to FIGURES 7 and 8, a cut-off attachment 60 is provided whereby a section of cable shield and dielectric may be removed to expose a premeasured length of center conductor. This is desirable in cases wherein the cable center conductor must project beyond the end of a cable. Attachment 60 includes a block having two arms 62 and 64 and a cable stop 66. Arms 62 and 64 extend beyond saw slot 12 on the outside of block 8 when the attachment is fastened to the block. This constitutes a stop to prevent the saw blade from bottoming in slot 12 and severing the center conductor of a cable. Stop 66 axially positions a cable relative to slot 12. Attachment 60 is secured to block 8 by screws 52 which extend through holes 65 in the attachment and into holes 53 of block 8.

In the use of attachment 60, block 8 with the attachment thereon is secured to a cable by cap 16 so that the cable end abuts stop 66. A saw blade is used in slot 12 to cut cable sheath 2 and dielectric 6. Screws 26 and 26 are then loosened sufiiciently to allow block 8 to be rotated about the cable for making subsequent cuts. The cable must be held against stop 66 while sawing to maintain correct axial position of the cut. After the cable sheath and dielectric are cut, block 8 is removed from the cable. The cut section of sheath and dielectric at the cable end is then pulled from the cable to expose a length of center conductor.

In the general operation of the fixture block and associate devices of the present invention, a cable end is positioned directly ahead (rightwardly in the drawings) of slot 12 in block 8. Cap 16 is fastened. to the block to secure the cable whereafter cap 18 is also fastened to pro vide a threaded opening in block 8. A saw blade, not

shown, is used in slot 12 to cut the end of the cable square and true.

Drill jig 30 is threaded into the block to align the cable center conductor and remove burrs. If the center conductor is to be drilled, a drill bit is then used. as described hereinbefore, whereafter jig 30 is theadedly removed. The tap jig 32 and tap 42 are next used to thread the inside of the center conductor whereafter jig 32 is removed from block 8.

In the case of a high voltage application, the preceding operations are performed after which cutter 44 is used in block 8 to cut a circular slot in the cable dielectric.

In specific cases wherein tests are to be made on precise lengths of cable, micrometer attachment 5G is used as described hereinbefore. After the use of attachment 50, the cable dressing operationsdescribed above are subsequently followed to theend of the cable.

It will, therefore, be understood that the cutting device disclosed herein is made of relatively fewv parts and is easy to use even in the field.

It will also be appreciated that the aforementioned and other desirable objects have been achieved; however, it should be emphasized that the particular embodiment of the invention, which is shown and described herein, is intended as merely illustrative and not as restrictive of the invention.

What is claimed is:

1. A cable cutting and dressing device comprising a block with a longitudinal passageway to receive a cable, means to secure said cable in said passageway, a thin slot in said block transverse to said passageway and extending fully therethrough for guiding a saw blade through cable placed in said passageway to permit an accurate cutting and facing of said cable, said block further including adjacent said slot further means to receive and secure attachments coaxial to said cable in said passageway for use in dressing the end of said cable after cutting and facing.

2. The device of claim 1 wherein one of said attachments includes means to align the end of the cable center conductor coaxial to the cable outer conductor after cutting, said means including a surface for facing said center conductor and an axial bore for centering drills and taps inserted into said center conductor.

3. The device of claim 1 wherein one of said attachments includes means to remove a portion of the cable dielectric surrounding said center conductor.

4. The device of claim 1 wherein one of said attachments includes a micrometer to accurately measure lengths of said cable to be removed.

5. The device of claim 1 wherein one of said attachments includes means to dress the end of a cable to expose a length of center conductor.

6. Apparatus for cutting and dressing the ends of coaxial electrical cable comprising a block adapted to be secured to a cable, means in said block for receiving a saw blade for accurately facing and cutting said cable, aligning means fitted and secured to said block for cating and centering the center conductor of said cable after cutting and for removing burrs therefrom, said aligning means including a bore for guiding drills into the cable center conductor whereby to prepare said cable for use with high frequency connectors.

7. Apparatus for cutting and dressing the ends of coaxial electrical cable comprising in combination a block having a cable receiving passageway therethrough and a saw receiving slot thereacross, cap means adapted to secure said block to said cable, aligning means in said apparatus for locating and centering the center conductor of said cable, means for receiving and guiding drills and taps into said center conductor for drilling and thread tapping operations on said center conductor, cutting means for removing select portions of cable dielectric, and micrometer means for measuring precise lengths of cable whereafter said lengths are removable from said cable by said saw blade.

8. A cable cutting and dressing tool for use in preparing coaxial cable comprising a block having a U-shaped passageway extending therethrough to permit installation on portions of cable apart from the ends thereof, means clamped to said block to secure said cable in said passageway, a transverse slot extending across said block and through said passageway to permit said cable to be cut into the formed end of said passageway having threads in the bottom surface thereof, further means adapted to be clamped to the formed end of said block, the said further means including a member extending into said passageway having threads complementary to the threads therein to deform a round threaded bore, an attachment for use in dressing the end of said cable having threads thereon mating with the threaded bore and adapted to be inserted therein against the cut end of the cable in said passageway.

No references cited.

RICHARD H. EANES, 111., Primary Examiner. 

1. A CABLE CUTTING AND DRESSING DEVICE COMPRISING A BLOCK WITH A LONGUTUDINAL PASSAGEWAY TO RECEIVE A CABLE, MEANS TO SECURE SAID CABLE IN SAID PASSAGEWAY, A THIN SLOT IN SAID BLOCK TRANSVERSE TO SAID PASSAGEWAY AND EXTENDING FULLY THERETRHROUGH FOR GUIDING A SAW BLADE THROUGH CABLE PLACED IN SAID PASSAGEWAY TO PERMIT AN ACCURATE CUTTING AND FACING OF SAID CABLE, SAID BLOCK FURTHER INCLUDING ADJACENT SAID SLOT FURTHER MEANS TO RECEIVE AND SECURE ATTACHMENTS COAXIAL TO SAID CABLE IN SAID PASSAGEWAY FOR USE IN DRESSING THE END OF SAID CABLE AFTER CUTTING AND FACING. 